Additive for minimizing cold sludge formation and lubricating oil containing the same



mg. m

peroxides and hydroperoxides.

United States Patent F ADDITIVE FOR MINllVIlZING COLD SLUDGE FORMATION AND LUBRICATING OIL CON- TAINING THE SAME Everett C. Hughes, Shaker Heights, and Harvey E. Al-

ford Amherst, Ohio, assignors to The Standard Oil Company, Cleveland, Ohio, a corporation of Ohio No Drawing. Filed Dec. 24, 1956, Ser. No. 630,052

2 Claims. (Cl. 252-18) This invention relates to lubricating oil additives useful in the preparation of lubricating oil compositions having a lessened or substantially no tendency to form cold sludge and increased water tolerance, and, more particularly, to lubricating oil compositions comprising an alkaline detergent, an antioxidant, and an oil-soluble polyoxyalkylene compound.

When an engine is operated during cold weather and in light duty stop-and-go operations, it rarely is heated to operating temperature for any substantial portion of the driving time. When the temperatures in the crankcase are below operating temperatures, contaminants enter the crankcase by way of blow-by. These contaminants are not dissipated because of the low operating temperatures of the oil, and have an opportunity to react or to catalyze reactions in the oil. These reactions result in the formation of what is called cold sludge, a black mayonnaise-like substance. One of the most important problems today is how to combat cold sludge, because most cars used in city driving are subjected to this type of driving conditions during cold weather.

It has now been determined that when an oil containing an alkaline sulfonate type detergent and a thiophosphate type antioxidant has added thereto an oil-soluble polyoxyalkylene compound, the oil does not develop cold sludge or keeps it dispersed when the engine is operated at low temperatures for long periods of time, and in addition has the increased water tolerance. ,It is thought that this additive is effective in minimizing cold sludge development because it destroys the contaminants which enter the oil. These contaminants are thought to include organic The peroxides are capable of catalyzing reactionsthat lead to the formation of high polymers, and it is believed that high polymers are major components of cold sludge. Accordingly, the efiectiveness of the additive of the invention is thought to depend upon its ability to react with peroxides to destroy them, and the additive has been evaluated on the basis of a screening test determining decomposition of cumene hydroperoxide at 100 F.

The increased water tolerance is thought to be due to an interplay between the sulfonate detergent and the oilsoluble polyoxyalkylene compound. It is believed that the sulfonate group is adsorbed by the solids dispersed The oil-soluble polyoxyalkylene compound is character 7 'ized by the following general formula:

ICC

in which R and R" are selected from the group consisting of hydrogen, alkyl and acyl groups having from four to about twenty carbon atoms, R is selected from the group consisting of hydrogen and alkyl groups having from one to about five carbon atoms, n is a variable small whole number from one to about four, preferably two or three, and may vary in this range even in a single long chain molecule, and y represents the number of repeating. units in the chain, and may be a whole number from about five to several hundred, depending on the molecular weight.

For the purposes of the invention the character of R and R", i.e., of the end groups of the chain, is not critical. Gum solvency properties of these compounds is attributed primarily to the oxyalkylene units which form the chain, and not to the end groups. However, although quite a wide variety of these compounds have gum solvency properties, only those with viscosities in the range of 50 to 5000 SSU at F. have the necessary non-volatility and oil-solubility characteristics. These compounds are prepared by condensation of the corresponding oxides, or oxide mixtures, such as ethylene or 1,2-propylene oxide, or mixtures thereof, as is set forth more fully in US. Patents Nos. 2,425,755 to Roberts et al., issued August 19, 1947; 2,425,845 to Toussaint et al., issued August 19, 1947; 2,448,664 to Fife et al., issued September 7, 1948; and 2,457,139 to Fife et al., issued December 28, 1948. If R or R" is alkyl, an aliphatic alcohol is incorporated in the reaction mixture, and if R or R" is acyl, an aliphatic carboxylic acid is incorporated in the reaction mixtures.

Compounds in accordance with the above general formula are available commercially under the trade name Ucon from the Carbide and Carbon Chemicals Corporation. The compounds available commercially may have a hydroxyl group at one end of the chain and an alkyl ether or ester group at the other end of the chain, such as those of Patents Nos. 2,425,755, 2,448,664 and 2,457,139, for example, a butyl group in the Ucon LB and DLB series, but it will be understood that for the purpose of the instant invention compounds having two terminal hydroxyl groups at each end of the chain, such as those of Patent No. 2,425,845, or having two terminal alkyl ether or ester groups at each end of the chain are suitable as Well. All three types of these compounds are intended to be covered by the generic term polyoxyalkylene compound as employed in the specification and claims.

It is essential that the polyoxyalkylene compound be oil-soluble, and have an SSU viscosity at 100 F. of from 50 to 5000. Compounds having a viscosity of less than 50 SSU are too volatile to serve as oil additives, while those having a viscosity of over 5000 SSU are too insoluble in lubricating oils to be suitable.

Very small amounts of the additives of the invention will give a marked improvement in lessening the formation of cold sludge. As little as 1.0% of the total additive mixture is effective, and amounts between 1.5% and 10.0% are preferred. Use of amounts in excess of 20.0% usually cannot be justified economically. Of the total additive mixture, the polyoxyalkylene compound is present in an amount within the range from two to sixteen parts by weight (p.b.w.). The barium octadecyl sulfonate is present in an amount within the range from 20 to 60 p.b.w., the barium carbonate in an amount within the range from 10 to 30 p.b.w., and the zinc octyl dithiophosphate in an amount within the range from 15 to 45 p.b.w.

The additives of the invention can be used to improve the cold sludge characteristics of any petroleum hydrocarbon oil of lubricating viscosity. The S.A.E. viscosities for lubricating oil range from No. 10 to No. 70. Oils Patented Dec. 13,1950

3 having S.A.E. Nos. 10 to 40 have a viscosity within the range from 90 to 255 SSU at 130 F., and those oils having S.A.E. Nos. 40 to 70 have a viscosity within the range firom 80 to 150 SSU at 210 F. The acid-treated and solvent-extracted oils are equally useful in the compositions of the invention. The oils can be blended from suitable bright stocks and finished neutral oils of light and heavy viscosities. It is impossible here to give a complete description of the various methods used in the preparation of lubricating oils, but reference is made to the text by Georgi, entitled Motor Oils and Engine The following example represents, in the opinion of the inventors, the best embodiment of their invention.

Example TABLE I A. NEW OIL Additive Vis- Spe- Alkacosity API citic Percent line SSU at Grav- Ash pH Numat 60 F. ity (80;) her 100 F.

2.25% mixture of: 40 p.b.w. barium octadecyl sulfonate;

20 p.b.w. barium carbonate; 28 p.b.w. zinc octyl dithiophosphate--. 222. 3 30. 5 0.8737 0.97 7. 24 1. 95 2.25% mixture of: 40 p.b.w. barium octadecyl sultonate; 20

p.o.w. barium carbonate; 28 p.b.w. zinc octyl dithiophosphate plus 0.25% monobutyl poly-1. 2-oxypropylene glycol having a viscosity of 385 SSU at 100 F. (Flexol 13-4 226.6 30.6 0.8730 0.90 8.0 1.69

B. USED OIL Vis. Inc. at Percent pH Acid 100 F. Ash Number SSU (304') Increase 2.25% mixture of: 40 p.b.w. barium octadecyl sulfonate;

20 p.b.w. barium carbonate; 28 p.b.w. zinc octyl dithiophnnnhah l +40. 1 0. 71 5. 1. 87 2.25% mixture of: 40 p.b.w. barium octadecyl sulfonate;

20 p.b.w. barium carbonate; 28 p.b.w. zinc octyl dlthiophosphate plus 0.25% monobutyl poly-1, 2-oxypropylene glycol having a viscosity of 385 SSU at 100 F. (Flexol B-40 22. 3 0. 91 5. 0 l. 98

Lubrication, published by Reinhold Publishing Corporation, New York (1950), chapter V, wherein the various types of lubricating oils are discussed fully. Any of the oils mentioned therein can be employed in the composition of the invention.

The composition of the invention is prepared simply by mixing the additives either singly or together with the oil, at room temperature. The additives are soluble or dispersible in the oil, and disperse therein instantaneously. No solvents are required.

The oils having the compositions listed below were tested for dispersancy and water tolerance.

The dispersancy test is a measure of the ability of the oil to hold carbon black dispersed. The oil to be tested is made up as a solution thereof in benzene, and 100 ml. of the solution is placed in a glass stopper-ed graduate. Carbon black in increments of 0.2 gm. is added to the solution, which is then shaken for fifteen seconds and permitted to stand for five minutes in front 50 of a light source and the contents observed for a break TABLE II Dlsnersancy Water Example Additive Percent Rating, g. Tolerance No. Carbon Rating,

Black ml. Water 1 A mixture of: 40 p.b.w. barium octadecyl sulfonate; p.b.w.

barium carbonate; 28 p.b.w. zinc octyl dithiophosphate 2. 8. 6 10 2 Monobutyl poly-L'zroxypropylene glycol having a viscosity of 385 SSU at 100 F. (Flexol B-400) 0.25 0 0 3 Examples 1+2 2. 25+0. 25 3. 6 100 TABLE III Dispersancy Water Example Additive Percent Rating, g. Tolerance No. Carbon Rating,

Black ml. Water 4 A mixtureof: p.b.w. barium octadecyl sulfonate; 20 p.b.w.

barium carbonate; 38 p.b.w. zinc octyl dithiophosphate 1. 5 3. 8 l0 5 Monobutyl poly-1.2-oxypropylene glycol having a viscosity of 385 SSU at 100 F. (Flexol B-400) 0. 1 0 0 d0 0.25 0 0 0. 5 0 0 Examples 4+" 1. 5+0. 1 4. 2 Examples 4+6. 1 5+0. 25 4. 4 Examples 4+7. '0. 5 4. 8 40 poin This point is seen as a thin upper layer of completely transparent liquid containing no carbon black particles. If no break point is observed, additional The test cycle was repeated 16 times for a total test duration of 96 hours. The sludge cycle test results are shown in Table V.

TABLE V Additive 2.25% Mixture of: 40 p.b.w. Barium Octadecyl Sulfonate: 20 p.b.w. Barium Carbonate; 28 p.b.w. Zinc Octyl Dithiophosphate EXAMPLE 12 2.25% Mixture of: 40 p.b.w. Barium Octadecyl Sulionate; 20 p.b.w. Barium Carbonate; 28 p.b.w. Zinc Octyl Dithiophosphate; Plus 0.25% Monobutyl Poly-1,2-Oxypropylene Glycol Having a Viscosity of 385 SSU at 100 F. (Flexol B400) EXAMPLE ll incremens of carbon black are added until there is a break point. The largest amount of carbon black which does not produce a break point is recorded as the result of the test. The test has been calibrated against various additive concentrations of dispersant additives in oil and is a measure of the dispersant or detergent properties of an oil.

The water tolerance test is an extension of the test previously described, and the solution of the oil is made up in the same way and has added to it an amount of carbon black equal to the dispersancy rating. Distilled water is then added in 10 ml. increments, and after each addition the flask is stoppered and shaken for fifteen seconds and allowed to stand five minutes. After this time, the suspension is similarly observed for a break point, and if none is observed an additional 10 ml. of water is added. This is continued until a break point is noted. The water tolerance test is important since an additive must not only have dispersant action in a dry oil but also in the presence of water because a crankcase in the winter often contains water as a result of condensation.

The dispersancy and water tolerance of the lubricating oil compositions were evaluated by the tests described.

The data show that the water tolerance and dispersancy of the barium octadecyl sulfonate-barium carbonate-zinc octyl dithiophosphate were greatly improved by addition of the polyoxypropylene glycol additive. The adata also show that the polyoxypropylene glycol is not a dispersant by itself, but in the presence of the other additive it has excellent dispersancy properties. Thus, a true synergistic effect is noted.

The oils were compared in the sludge cycle test. This test is conducted in a six cylinder Chevrolet engine, unloaded, at the following cycles.

It will be noticed that the precipitated sludge of EX- ample 12 is much smaller, as are the total insolubles in oil. This is a significant difierence.

In view of the above examples, other embodiments will be apparent to one skilled in the art and are embraced in the following claims.

We claim:

1. An additive for a mineral lubricating oil for the lessening of cold sludge formation in operation of a lubrieating oil at low temperatures, consisting essentially of from 20 to 60 parts by weight barium octadecyl sulfonate, from 10 to 30 parts by weight barium carbonate, from 15 to 45 parts by weight zinc octyl dithiophosphate, and from 2 to 16 parts by weight of an oil-soluble polyoxyalkylene compound having the formula in which R and R are selected from the group consisting of hydrogen, alkyl and acyl groups having from four to about twenty carbon atoms, R is selected from the group consisting of hydrogen and alkyl groups having from one to about five carbon atoms, n is a variable small whole number from one to about four, and y represents the number of repeating units in the chain to provide a viscosity of 50 to 5000 SSU at F.

2. A mineral lubricating oil composition consisting essentially of a mineral lubricating oil and an amount of an additive in accordance with claim 1, within the range from 1% to 20% sufiicient to lessen cold sludge formation and increase water tolerance during operation of the oil at low temperature.

References Cited in the file of this patent UNITED STATES PATENTS 2,369,632 Cook et al. Feb. 13, 1945 2,451,345 McNab Oct. 12, 1948 2,501,731 Mertes Mar. 28, 1950 2,623,016 Mertes Dec. 23, 1952 2,671,758 Vinograd et al. Mar. 9, 1954 2,676,925 Lindstrom et al. Apr. 27, 1954 2,839,469 Pfeifer June 17, 1958 UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No, v 2,964,473 December 13, 1960 Everett C. Hughes et a1 It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Columns 3 and 4, TABLE I, under the heading "USED OIL", first column thereof, for "+40. 1" read -40. l column 5, line 59, for "adata" read data q Signed and sealed this 4th day of July 1961.

(SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents 

1. AN ADDITIVE FOR A MINERAL LUBRICATING OIL FOR THE LESSENING OF COLD SLUDGE FORMATION IN OPERATION OF A LUBRICATING OIL AT LOW TEMPERATURES, CONSISTING ESSENTIALLY OF FROM 20 TO 60 PARTS BY WEIGHT BARIUM OCTADECYL SULFONATE, FROM 10 TO 30 PARTS BY WEIGHT BARIUM CARBONATE, FROM 15 TO 45 PARTS BY WEIGHT ZINC OCTYL DITHIOPHOSPHATE, AND FROM 2 TO 16 PARTS BY WEIGHT OF AN OIL-SOLUBLE POLYOXYALKYLENE COMPOUND HAVING THE FORMULA 